1. Field of the Invention
This invention relates generally to measurement of the eye and construction of eye models based on such measurements.
2. Description of Related Art
In the past decades, a variety of generic optical models for the human eye have been established to facilitate the diagnosis and treatment of ocular diseases. However, as a complicated imaging system, each individual eye has its own physiological characteristics. Characterizing the optical parameters of an individual eye is crucial for applications such as assessing wound healing after corneal refractive surgery and optimizing eye glasses or contact lenses.
To construct an individual eye model, typically three ocular surfaces are modeled: the anterior surface of cornea, which is responsible for ˜70% optical power of the eye, and the anterior and posterior surfaces of the crystalline lens, which are responsible for the remaining ˜30% optical power of the eye. The individual eye model can be established in vivo by combining three techniques: corneal topography, wavefront aberration measurement, and numerical modeling. Conventionally, the corneal surface curvature is acquired by either using a Placido disc (e.g., Zeiss ATLAS corneal topography system), or using a scanning slit (e.g., Orbscan corneal topographer), or Scheimpflug photography (e.g., Pentacam corneal topographer). The wavefront aberration is typically measured using a Hartmann-Shack sensor (e.g., Zeiss i.Profiler wavefront analyzer). However, the reliance on multiple costly instruments limits the accessibility of constructing an individual eye model to the general ophthalmologists. In addition, because the conventional corneal topography techniques rely on scanning, 1-2 seconds are typically required in order to complete the measurement. The movement of the eye during this process may introduce motion artifacts.
In addition, plenoptic imaging can be used to estimate depth based on disparity measurements. However, in plenoptic three-dimensional imaging, a prior disparity-to-depth calibration is generally required in order to reconstruct the objects' depths. Typically during calibration, a grid or point target is placed in front of the plenoptic imaging system and scanned along one axis (in case of grid target) or three spatial axes (in case of point target). However, when imaging the eye, such a procedure cannot be used because the eye's crystalline lens is also a part of the imaging system and we cannot simply put a target with “known” depth inside the individual's eye.
Thus, there is a need for better approaches to making eye measurements used to construct an individual eye model.